#0E172B

CSS

:root {
  --sombre-night: #0e172b;
  --sombre-night-rgb: 14 23 43;
  --sombre-night-oklch: oklch(0.208 0.042 264.7);
}

.element {
  color: var(--sombre-night);
  background-color: hsl(221 51% 11%);
  border-color: oklch(0.208 0.042 264.7);
}

Tailwind CSS v4

@theme {
  --color-sombre-night: #0e172b;
  --color-sombre-night-50: #f0f5ff;
  --color-sombre-night-100: #e1e8f7;
  --color-sombre-night-200: #ccd4e7;
  --color-sombre-night-300: #adb7ce;
  --color-sombre-night-400: #929fb8;
  --color-sombre-night-500: #7886a3;
  --color-sombre-night-600: #66728a;
  --color-sombre-night-700: #515b6e;
  --color-sombre-night-800: #3b4351;
  --color-sombre-night-900: #282e39;
  --color-sombre-night-950: #161b23;
}

SCSS

$sombre-night: #0e172b;
$sombre-night-rgb: 14, 23, 43;
$sombre-night-light: mix(#fff, $sombre-night, 20%);
$sombre-night-dark: mix(#000, $sombre-night, 20%);

.element {
  color: $sombre-night;
  box-shadow: 0 0 0 2px rgba($sombre-night, 0.35);
}